The present invention relates to a dust preventing device for an electromagnetic contactor, wherein foreign matters are prevented from entering into an electromagnetic contactor through a gas discharging opening.
FIGS. 7 through 9 show a structure of a conventional dust preventing device, wherein FIG. 7 is a vertical section view of a principal part around a contact portion of the electromagnetic contactor; FIG. 8 is an enlarged perspective view of a principal part of an arc extinguishing chamber cover; and FIG. 9 is a perspective view of an outer appearance of the electromagnetic contactor shown in FIG. 7 when installed.
In these figures, reference numeral 1 designates a fixed contact, and 2 represents a movable contact which is attached to and detached from the fixed contact 1. The contact 1 is fixed to an upper case 3, while the movable contact 2 is supported by a movable contact support 4 which slides in the horizontal direction, in FIG. 7, in the upper case 3 and is urged by a contact spring 5. The fixed contact 1 and the movable contact 2 have a fixed contact point 1a and a movable contact point 2a, respectively, in respective opposing surfaces. The fixed contact 1 includes a terminal screw 6 at its end.
The movable contact support 4 moves together with a movable core (not shown), so that when the movable core is sucked, the movable contact 4 is moved in the right horizontal direction in FIG. 7 to thereby cause the movable contact point 2a to contact the fixed contact point 1a. Reference numeral 7 represents an arc extinguishing chamber cover to cover a switching space. Arc extinguishing partitions 9 extend for the respective parts from a sealing wall 8 for covering top portions of the movable contact support 4. The arc extinguishing partition 9 includes a gas discharge opening 10 in a rectangular shape. Reference numeral 11 designates a foreign matter preventing wall which is provided in the electromagnetic contactor so that foreign matters do not enter thereinto through the gas discharging opening. The foreign matter preventing wall 11 is formed in a rectangular shape to coincide with the shape of the gas discharging opening 10 in a mounted posture as shown in FIG. 8. Further, the foreign matter preventing wall 11 is formed parallel to the arc extinguishing partition 9 with an appropriate space therebetween, and integrally with the sealing wall 8.
With such a structure of the conventional extinguishing contactor, when foreign matters enter into the gas discharging opening 10, and if foreign matters are larger than a space between the arc extinguishing partition 9 and the foreign matter preventing wall 11, such foreign matters are prevented from entering into the extinguishing contactor. On the other hand, if foreign matters are smaller than the space, such foreign matters cannot be prevented from entering thereinto. More specifically, in case foreign matters with insulating ability enter between the fixed contact 1 and the movable contact 2, there may occur a difficulty in conductivity, while when foreign matters with magnetism enter into a space between the fixed contact 1 and the movable contact 2, the magnetic foreign matters are sucked by magnetism of an electromagnet and adhered to the contact surfaces, which results in a problem such as buzzing.
Accordingly, an object of the present invention is to obviate the above problems and to provide a dust preventing device for an electromagnetic contactor, wherein prevention of foreign matters from entering or invading into the space between the arc extinguishing partition and the foreign matter preventing wall is effectively improved.